Implantable medical devices are used to monitor physiological parameters and to deliver therapy to selected organs. An external programmer is often used by physicians to communicate data with an implantable device. The data may include measured parameters, electrocardiograms, markers, instructions, identification information and other such data. Typically, the external programmer includes a near field loop antenna that is positioned near the implantable device and an inductive coupling allows data communications. Because the external antenna is close to the patient, it can be assumed that the programmer is authorized to exchange data with and program the implantable device.
With the advent of far field communications for implantable devices, unauthorized or unintended communications with an implantable device becomes possible. Such communications can result in a minor inconvenience or tragic, life threatening, consequences.